Microcavity plasma devices spatially confine a low temperature, nonequilibrium plasma to a cavity with a characteristic dimension d below 1 mm, and as small as 10 μm×10 μm. Researchers at the University of Illinois have developed and demonstrated a range of microcavity plasma devices and arrays of microcavity plasma devices. A number of fabrication processes and device structures have advanced the state of the art and provided devices and arrays in a variety of materials including, for example, semiconductors, ceramics, glass, and polymers. Arrays of microcavity plasma devices that have been developed include addressable arrays. Devices can be operated at high pressures (up to and beyond atmospheric pressure), thus simplifying the requirements for packaging an array. Plasma display panel technology, on the other hand, requires a partial vacuum in the display which requires accordingly sturdy packaging to protect the panels. The various microcavity plasma devices and arrays that have been developed to date have broad utility, with certain ones being especially suited toward one application or another, including for example, general lighting applications, displays (including high definition displays), medical therapeutic procedures, and environmental sensors.
Previous microcavity plasma devices have been turned on and modulated, if modulation was desired, by varying the full voltage across the io device. The RMS value of this voltage is typically 150 V or more. Switching high voltages directly requires relatively expensive driving electronics. Current commercial plasma display panels, which do not use microcavity plasma devices, switch high voltages, for example. The circuitry for switching the high voltages represents a significant cost in the manufacturing of existing plasma televisions, for example. The expense does not arise from the need to apply a high voltage (say, 150 V) to a pixel in a display, but rather from the need to vary it (modulate) quickly in response to a video signal. The need for high speed and high voltage has a serious (negative) impact on the cost of the electronics and the plasma display panel.
Researchers at the University of Illinois have previously developed field emission assisted microcavity plasma devices, which are disclosed in U.S. Pat. No. 7,126,266 (the '266 patent), which issued on Oct. 24, 2006. The field emission nanostructures disclosed in the '266 patent are integrated into microcavity plasma devices or situated near an electrode of microcavity plasma devices and serve to reduce operating and ignition voltages, while also increasing the radiative output and efficiency. The field emission nanostructures in the '266patent include carbon nanotubes and other similar field emission nanostructures, such as nanowires composed of silicon carbide, zinc oxide, molybdenum and molybdenum oxide, organic semiconductors or tungsten. The field emission structures in the '266 patent is they cannot be controlled separately from the microplasma devices themselves. The field emission structures emit electrons as long as the microcavity plasma device is in operation. The inability to readily control nanotube and nanowire electron emission renders these nanostructures of limited value in reducing the voltage necessary to modulate a microplasma device.